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There are about 3,000 known
minerals, only about 30 are
common.
The most common are
quartz,feldspar,mica, and calcite.
These minerals make up most of
the rocks found in the Earth’s
crust.
Most of the Earth’s crust is made up
of feldspar, followed by quartz and
mica.
So what is a mineral?
What are the characteristics of
all minerals?
What is a mineral?
Mineral- A mineral is a naturally formed,
inorganic solid with a crystalline structure.
Rocks are actually made of many minerals but
minerals are not made of rocks.
1. A mineral occurs naturally.
2. A mineral is solid.
3. A mineral has a definite chemical
composition.
4. A mineral’s atoms are arranged
in an orderly pattern.
5. A mineral is inorganic (was never
alive)
To be able to identify these and
other minerals, we need to look at
the properties used to separate
and distinguish these minerals.
Remember!:
Rarely is a mineral identified by a
single property.
These properties need to be
considered together to correctly
identify a mineral.
Mineral properties
►Color
►Luster
►Cleavage
►Streak
►Hardness
►Other
& Fracture
Color is the most easily observed
mineral property and the least
useful!
Many minerals have a similar
color.
Many minerals can turn colors
due to impurities. They may
also have a mottled appearance
or wavy appearance.
For example, pure quartz is
colorless or white, impurities
can make the mineral rose,
purple or pink!
Luster refers to the way a
mineral shines in reflected light.
Notice the difference between
these two minerals?
The mineral on the left has a
metallic luster (looks like a metal),
the one on the right, a nonmetallic
luster (does not look like a metal).
Certain minerals have a metallic luster, such
as silver, copper and gold. Minerals that do
not reflect light have a nonmetallic luster,
and are described by terms like glassy,
pearly, dull and silky.
Other terms that might be used include
greasy, dull, and earthy.
Streak of a mineral is the color of its
powder when rubbed on an
unglazed white tile.
The streak is often not the same
color as the mineral.
A minerals color may vary, but the
streak rarely will!
Color of streak.
A mineral may not leave a streak.
The cleavage of a mineral is how it
breaks.
Observations:
Cleavage – if it looks like it has been
cut, flat surfaces
Irregular – does not have a clean
break
Mica is probably the best example as
it splits into thin sheets. It is said
to have one perfect cleavage.
Feldspar splits readily in two
directions, always at or near right
angles.
Cleavage & Fracture
Best identified on a fracture surface
How resistant the mineral is to
being scratched.
(scratch test!)
Diamond is the hardest of all minerals, and
talc is the softest.
Friedrich Mohs devised a hardness
scale.
In this scale, ten well known
minerals are given numbers from
one to ten.
Talc (left) is the softest and has a
hardness of 1. A soft pencil lead will
scratch talc.
Gypsum is a bit harder and has a
hardness of 2. A fingernail scratches
gypsum.
Calcite (left) has a hardness of 3 and a
copper penny just scratches it.
Diamond with its hardness of 10 can
easily scratch the rest of the minerals.
Use Mohs’ Scale. Does it scratch with a
finger nail? Penny? Nail?
Would a fingernail scratch calcite?
NO
Would a steel nail scratch orthoclase?
NO
Would a copper penny scratch talc?
YES
Would a copper penny scratch fluorite?
NO
Would a fingernail scratch gypsum?
YES
Crystal shape can be a useful
property to identify minerals if the
minerals have had the time and
space to form crystals. Most
mineral grains that are found in
rocks, lack the room to grow.
Magnetic
Malleable
Radioactive
Flourescence
Taste
Halite (rock salt)
can be identified
by its taste.
This practice is not
recommended!
This is the state of
glowing while
under a ultraviolet
light.
Some minerals even
glow once the light
is turned off!
Some minerals, such
as this uraninite,
are radioactive.
They give off
subatomic particles
that will activate a
Geiger counter.
Some minerals
that contain
Iron, are
magnetic and
can be picked up
by a magnet.